Tricolor television picture tube



July 31, 1956 T. MILLER 2,757,313 TRICOLOR TELEVISION PICTURE TUBE Filed June 2l 1951 Fig. 3.

' Fig.2.

f/ @Q7/M Theodore Miller.

g k/mm@ ATTORNEY United States 2,757,313 TRICOLOR vrELlsvrsioN Piernas TUBE Application June 21, 1951, Serial No..232,"798 s Claims.l (c1. 315-13) My invention is directed .to television systems in general, and more .particularly is concerned with improveyments rin color television reproduction systems.

.Inaccordance with vthe prior art color-television receiver .apparatus with which I am familiar, the provision of light emitting .phosphor strips, which are arranged horizontally .to makeup a cathode-raytube screen is Well known.V How- `over, a .problem is presented when yan electron ybeam is employed to .energize ythese phosphor strips, in that the .present vertical sweep -c'ircuits are not sufficiently free `from disturbingsinuences, such that the electron beam vmay be made .tosweep accurately respectingfthe vertical movement of the beam. In actual practice there is a tendency .for the beam .to `follow a 'path which deviates from `the particular horizontal ,phosphor strip which is to be scanned. This tendency results in the electron beam,

which is .manning -a k.particular vhorizontally positioned phosphor strip, swaying-from its desired path, such that it willenergize one of the `adjacent phosphor strips, either .energizing the .strip .above or the strip below the one .desired .It is ,customary to arrange lthe horizontally positioned ,phosphor strips vinto Lalternate red, green and blue color ,producing strips. .A singleelectron beam, or a'tripleelectron beam, cathode ray tube .may be provided for Ithe energ'i'zat'ion of the respectivered, green .and-.blue-phosphor strips. To .obtain asatistactory reproduced picture resolution, `it .'is desirable .to .utilize .a relatively .large ynumber of comparatively thinphosphor strips, i. e., such asa thousand phosphor strips, .each being .in .the .order-.of .5 -mils wide. When such a picture screen :is employed,.it is necessary to maintain the vertical-.position registry -of ltheelectron Abeam or 4-beams `.to within a yery few mils rof their proper -position, i. e., centered on Athe particularphosphor strip which 'isbeinjg scanned. If thelatter condition is `not maintained, objectionable color degradation is obtained, since a shift of merely '5 mils is sufficient to completely destroy Ythe original color .values of the televised -video signal.

Accordingly, lit-is an object of my invention toprovide a continuous and automatic :position registry `correction apparams.

It 'is another object of my invention to insure proper 'color *phasingA in a color television picture ytube.

It is affurther object of my invention to provide a sweep correction circuit for assuring the .properscansion movementor an Velectron beam along particularlya horizontally positioned jand relatively thin ,phosphor strip.

`It is a lstill further object of my invention .to prevent color degradation in the reproduced color television pictture.

It "is a still additional object of my invention. to maintainpar'ticularly the vertical position ofan .electron beam :when it 'is energizing a relatively thin and horizontally i positioned phosphor strip to Within a fraction of the strip width and near .the desired .position for ,the electron beam.

Myfinvention comprises lthe yprovision and arrangement of p'hosp'hor 'materials vinto Ygroups of red, green and blue vcolor-producing phosphors, to make up the Ytarget .screen vfor a color .television picture tube. Strips `of 'electrically conductive material are placed on the respectively opposite sides vof a particular phosphor strip in each group, .such as .the strip used for the reproduction fof one .of a .plurality of the predetermined primary colors. For example, a strip of conducting material is placed -on .the respectively opposite sides Yof. the red phosphor strip in each group, where Lthe group .comprises a phosphor strip .for the reproductionof red, green and blue colors. Then acommonbus wire is positioned `on each side ofthejpicture tube screen, the strips of `conductive material on the upper side of the red phosphor strip being connected .to one-of said bus wires and the strips of .conductive material located at the underside of `each said phosphor lstrip being vcon- .nected to the other bus wire. Each -of -the bus wires =is .connected to apply a position correction signal to the deflection means for the electron beam or beams, employed for the energization of the red, green .and blue Vphosphor strips. Itis to be understood .that the .green or blue phos- ,phor strips may `also .be used for .this purpose.

The respective groups of phosphor strips -may Vbe physically separated .by a greater amount than the physical .separationbetween the individual phosphor strips in each group, such .that ythe electron beam position relative to .the red phosphor strip in each group may be fcontrolling .over .the .electron beam .position for each of `thegroups -of .phosphor strips, However, asa preferred modification-of my invention, thephysical spacing between groups of phosphor strips Ymay be substantially the same as the 4physical .spacing between the .individual Vphosphor strips of `each group, with a modulation signal lbeingfappliedvtothe-electron beam when it is scanned `relative .to' the red phosphor strip, .if .a single Lelectron beam picture .tube .is employed. Or a modulation sign-al `may be 4continuously :applied 'to :the .electron beam which is employed for the energization of .one of .the yphosphor strips, forexample, :the red 'phosphor strip, when a multiple-electron beam picture tube .is used.

.The novel features that I consider characteristic -of .my invention are set forth with particularity in 'the appended claims. The invention itself, however, both as to its-organization .and method of operation, together `with l.additional objects andad-vantages thereof will best `be understood .from the following description of :specific 'embodi- .ments when read in `connection with the accompanying drawing, in which:

Figure l `shows a color television :picture tube vin .accordance with my .invention having a Ascreen made up of red, green and blue phosphor strips in eachfof a'plurality .of groups, with yan electron beam being lprovided for the .energizationofeach of the phosphor strips inthe 'respective groups.

Fig. .2,shows `an end view .of Aa portion of the picture ltube .screen shown in Fig. l, with Fig. 2 showing-.the interlaced lconductive members positioned on Veither side lof the red phosphor strips, and .connected ythrough the com- .mon bus wires to a vacuum tube ybridge circuit arrangement, .the latter vbeing adapted for connection to '-Zthe `devtlection means for controlling .the position :of -the -enervgizi'ng electron beams.

Fig. 3 shows a modified screen arrangement, with .a space being provided von each side ofaprechosen phosphor strip.v Y

Referring in particular to theapparatus shown in.Eig..-1, a color television vpicture tube .l0 of the cathode-raytube type is .provided having an .electron gun 12:.adapted for-the provision of three electron beams. .A (target screen.1-4.is provided for the picture .tube 10, .said yscreen v148 being made up of a plurality .of .phosphor strips `arranged anto groups of respectivelyred, The target screen 14, as illustrated in Fig. l, is greatly green and blueiphosphor strips.

vmay comprise a great The target screen in actual practice many of these phosphor strips in the order of a thousand or so of them each in the order of 5 mils wide. A deflection means 16 is provided along the path of the electron beams, such that the impingement position of the latter beams relative to the target screen 14 may be controlled.

The electron gun 12 of the picture tube 10 comprises a cathode 46, a control grid 48, 50, 52 for each of the electron beams generated, a focus grid 54 and an anode member. As illustrated in Fig. l, the control grid 48 for one of the electron beams is provided with a `source of high frequency modulating signals such as a high frequency oscillator 18, the latter being connected to the control grid 48 for the electron beam which is to accomplish the energization of a particular one of the phosphor strips in each of the groups. A plate 47 having a plurality of apertures or openings therein is employed for the generation of a corresponding plurality of electron beams; the latter beams being emitted from the surface of the cathode 46 and passing respectively through the apertures in plate 47.

In Fig. 2 is shown an end view of the target screen 14 with the horizontally positioned red 56, green 58 and blue 60 phosphor strips greatly magnified in size for the purpose of better illustration. In actual practice this screen will be of the type well known to those skilled in this art. Strips of conductive material 20 and 22 are positioned on either side of one phosphor strip, such as, for example, the red phosphor strip 56, the alternate strips of conductive material being connected to common bus wires 24 and 26, which are connected to the control grids 62 and 64 of a pair of triode tubes 28 and 30 that are arranged as components of a balanced bridge circuit 32.

In the bridge circuit 32, the anodes 66 and 68 of the latter triode tubes 28 and 30 are connected together through a pair of respective resistors 70 and 72 and then to a source of B+ voltage 74. The cathodes 76 and 78 of the latter tubes 28 and 30 respectively are connected together at a common junction. The previously described common bu-s wires 24 and 26 are connected to the respective control grids 62 and 64 of the triode tubes 28 and 30 through lter circuits 34 and 36, which are tuned to the frequency of the applied modulation signal from the modulation supply high frequency oscillator 1S shown in Fig. 1. A grid bias circuit 86 and 88, respectively, is provided for each of the tubes 28 and 30 comprising a series connected bias resistor and capacitor and a second capacitor shunting the bias resistor. The latter components are provided to insure sufficient grid bias for the desired operation of the tubes. The output of the bridge circuit 32 is applied through leads 38 and 40 to the deection control means, illustrated as detlection yoke 16, of the provided picture tube 10.

In Fig. 3 is shown red 80, green 82 and blue 84 phosphor strips arranged into respective groups, with conductive members 42 and 44 placed on each side of one strip, shown as the red phosphor strip 80 for illustrative purposes. If the beam (or beams) strays from this red phosphor strip 80 in either an upward or downward direction, the beams from the green 82 and blue 84 strips will not energize the conductive members 42 and 44 on either side of the red phosphor strip 80 due to the physical spacing of the latter strip 80 and its adjacent conductive members 42 and 44 relative to the green 82 and blue 84 phosphor strips.

In the operation of the picture tube shown in Fig. l, a single electron gun 12 is provided for the generation of three equally spaced electron beams which may be deflected by a deflection yoke 16, the respective electron beams impinging upon a target screen 14 comprising groups of alternate red, green and blue phosphor strips arranged horizontally. The design of such a picture tube 10 is considered to be well known to those skilled in the art. Each of the electron beams is modulated by a conmagniied in size.

trol grid with the respective red, green and blue televised video information.

In the normal operation of the tube 10, the deilecting yoke 16 receives sweep signals from provided sweep circuits in the television receiver, of which the illustrated picture tube 10 is a component part, for the scansion of each of the electron beams along its respective red, green, or blue phosphor strip. The latter strips are in each of the groups which make up the over-all target screen of the picture tube 10, and the electron beams horizontally scan the phosphor strips from one side of the target screen 14 to the opposite side of the target screen 14.

If the path of the electron beam remains on the respective phosphor strip, which is being scanned by any one of the three electron beams, no correction signal is detected by the provided strips of conducting material 20 or 22, and the provided balanced bridge circuit 32 remains unchanged, lsuch that the latter circuit 32 gives a zero output. Hence, in this case, the bridge circuit does not apply a correction signal through the deflection yoke 16 to correct the position of the electron beams on the horizontal strips of the target screen 14. However, if the path of the beams should tend to stray from that desired for the scansion of the phosphor strips, the strips of conductive material 20 and 22 will receive energy from particularly the electron beam which is scanning the red phosphor strip 56, and has the high frequency voltage modulated on it, and apply the proper correction signal from the balanced grid circuit 32 through leads 38 and 40 to the deflection yoke 16 for the correction of the electron beam position.

In accordance with a preferred embodiment ofv my invention and with the phosphor strip arrangement illustrated in Figs. 1 and 2 of the drawing, a high-frequency modulating signal is applied to the electron beam energizing one of the phosphor strips, such as for example, the red phosphor strip 56, and if this electron beam strays from the latter phosphor strip 56, it will strike one of the adjacent strips of conducting material 20 or 22 to unbalance the provided bridge circuit 32. For example, if the electron beam should stray in an upward direction, the strip of conductive material 20 placed above the red phosphor strip 56 will receive energy from the electron beam. This energy will then be applied to one of the triode tubes 28 through the provided iilter circuit 34. This unbalances the otherwise balanced circuit 32 such that a correction signal is applied to the deection yoke 16 for correcting the impingement position of the electron beams (or beam, if a single beam tube is used) relative to the phosphor strips being scanned. On the other hand, if the path of the electron beams tend to leave the phosphor strips in a downward direction, the strip of conductive material 22 below the red phosphor strip 56 will apply to the control grid 64 of the other triode tube 30 a signal corresponding to the high frequency modulation carried by the electron beam for the red phosphor strip 56. This unbalances the bridge circuit 32 such that a correction signal is applied to the detiection yoke 16 for elevating and hence correcting the impingement position of the electron beams relative to the phosphor strips.

As a modiiication of my invention, and as illustrated in Fig. 3, the source of modulating voltage 18 may not be employed, and instead the physical spacing between the groups of phosphor strips, and the red strip relative to the others 82 and 84 may be made greater than the physical spacing between the respective green 82 and blue 84 phosphor strips in each of said groups. In other words, one of the strips is eiectively separated from the other strips by a predetermined physical separation. In this arrangement the strips of conductive material 20 and 22 may be placed on respectively opposite sides of the so physically separated one 80 of the phosphor strips in each of said groups. For example, the

red phosphor strip 80 may be the one separated from the other strips. If the strips in each of the groups are arranged in red, green and blue order, or in any order, it may be preferable that the red phosphor strip 80 be arranged as the outermost strip in each group. The impingement position of the electron beam, for the red phosphor strip 80, which is the strip having the conductive strips 42 and 44 on each of its sides, may be used to control the position registry of all the electron beams, when a multiple beam tube such as shown in Fig. l is employed, or of the beam if a single beam tube is used.

For example, with the strips of conductive material 42 and 44 yplaced on respectively opposite sides of the red phosphor strip 80, when the three correspondingly spaced electron beams tend to wander from the phosphor strips in an upward direction, the electron beam which energizes the red phosphor strip 80 will strike the upper conductive material strip 42 before the electron beam for the green strip strikes conductive strip 44, and hence through strip 42 there is applied a correction signal to the -dellection yoke 16 which will lower the electron beams .such that they are again properly registered in position relative to the phosphor strips. On the other hand, if the electron beams tend to wander in a downward direction, a correction signal is applied from conductive strip 44 through the deliection yoke 16 to elevate the beams back to the desired position for properly scanning the horizontal phosphor strips. The bridge circuit 32 for the latter modication of Fig.

3 is the same as that illustrated in Fig. 2. However,l

the tuned lters 34 and 36, which are provided in Fig. 2 in the outputs of each of the common bus wires 24 and 26, will not be necessary with the modification of Fig. 3 since a high frequency Voltage is not modulated on any of the electron beams.

To improve the stability of the system, it is desirable to maintain the correcting potentials that appear at the end of the horizontal sweep during the horizontal retrace time. This may be accomplished by properly selecting the time constant for the parallel RC grid circuits of the provided triode tubes 28 and 30 in the bridge circuit 32. Since the vertical sweep circuit is a relatively low frequency circuit and involves a large inductance, the time rate of the undesired beam fluctuations, in particularly the vertical direction, will be considerably smaller than the horizontal retrace time. Accordingly, 4it is practical to use an R. C. time constant which is substantially equivalent to the horizontal retrace time.

While I have shown and described certain specific embodiments of my invention, many modifications thereof are possible. For example, the strips of conductive material may be applied to the target screen by methods such as those involving the well known printed circuit techniques. It is to be further understood that to prevent picture distortion, the modulation voltages applied to the predetermined one of the electron beams should be relatively high in frequency compared to the picture resolution of the screen. The use of my invention with a dot or similar arrangement of such substances is considered to be within the scope of my invention. By the terminology of red, green or blue phosphors, it is intended to mean and refer to phosphor or similar materials which may be employed to produce these colors of light. Also, the blue phosphor material may be more desirable than the red phosphor material, as the one to be used for correction purposes, in that the change in the average luminosity produced by the modulating voltage applied to this electron beam will be much less noticeable if it is introduced on the electron beam which scans the blue phosphor. In this respect the human eye is less sensitive to luminosity changes in the blue color, than it is to similar changes in red or green colors. Further, it is to be understood that with the modified screen arrangement shown in Fig. 3, the electron beams, where a multiple beam tube is employed, will be spaced 6 corresponding to the separation between the phosphor strips of the screen. Therefore, my invention is not to be restricted except as is necessitated by the prior art and the spirit of the appended claims.

I claim as my invention:

l. ln color television apparatus, the combination of a cathode ray tube having a `screen including a plurality of light-emitting substances, one of said substances having a finite Vlength being provided for each of a plurality of colors to be produced, said tube having an electron beam for selectively energizing each of said substances, a first conductor member on a first side of one of said substances, and having substantially the same length as said latter one of said substances, ka second conductor member on -the second side of said latter substance, means for impressing an image signal comprising components within a predetermined frequency range on said electron beam, a sourceof auxiliary modulation voltage of predetermined frequency loutside of the range -of vsaid image signals, said auxiliary modulation applied lto modulate said electron beam, detection means connected Vto said conductors 'for detecting said auxiliary modulation voltage on said electron beam and means for deriving a signal from said detection means for correcting the registration of said electron beam when it is not properly registered for the energization of respective light emitting substances.

2. In color television apparatus, the combination of a cathode ray tube having a screen including a plurality of light-emitting substances, each having a finite length and comprising a phosphor material, and one of said phosphor materials being provided for the reproduction of each of a plurality of predetermined colors, said tube having an electron beam for selectively energizing each of said 'phosphor materials, a tirst and a second conductor member on respectively opposite sides of one of said phosphor materials, said tirst and second conductor members having substantially the same length as the length of said one of the phosphor materials, means for impressing an image signal comprising components within a predetermined frequency range on said electron beam, a source of auxiliary high frequency modulating signals of predetermined frequency outside the range of said image signals, said auxiliary signals being applied to modulate said electron beam, detection means connected to said conductors, said detection means being sensitive to said auxiliary high frequency modulating signals, and deflection means connected to said detection means to receive a correction signal if said beam impinges on either of said conductor members.

3. In a color television receiver apparatus, the combination of a cathode ray tube having a screen including a plurality of light-emitting substances, each of said substances having a finite length' and being in the nature of a phosphor material, one of said phosphor substances being provided for the reproduction of each of a plurality of predetermined primary colors to be reproduced, said tube having a plurality of electron beams, each of said beams being adapted for the energization of a different one of said phosphor substances, a first and a second electron sensitive strip placed on respectively opposite sides of one of said phosphor substances, said first and second electron sensitive strips extending along said one of the phosphor substances for substantially the whole of said finite length, a source of high frequency modulating signals, said signals being applied to modulate said one of said electron beams, detection means connected to said electron sensitive strips and sensitive to said high frequency modulation signals, deflection means for the electron beams, said deection means being connected to said detection means to receive a correction signal if the latter electron beam impinges on either of said electron sensitive strips.

4. In a color television receiver apparatus adapted for the reproduction of a televised picture in a plurality of predetermined colors, the combination of a cathode ray tube having a plurality of electron beams, said tube having a target screen made up of a plurality of light-emitting substances, yone of 'said substances being provided for each ofy said colors and one of said ybeams being provided for each of said substances, a source of predetermined frequency modulation voltage, the latter being applied as a modulation to one, of said electron beams, and detector means adjacent said target screen for detecting said y respectively opposite sides of aparticular one of saidy phosphor material strips, delection'means being provided for the electron beam which energizes the latter phosphor iny material strip,

to the latter deflection means. f

References Cited in the tile of this patent UNITED STATES PATENTS Swedlund Aug. 3, Munster et al. Jan. 4, Sunstein Feb. 15, Meacham June 21, Huffman Dec. 13, Harrison Sept. l2, Huffman Nov. 21, Weimer Mar. 13, Snyder Oct, 16, Schultz et al. f Dec. 4, Law July 1, Muller Mar. 3, Nicoll Mar. 10, Bradley July 7,v Parker y Oct. 27,

said conductor members being connected 

